Search Results (203)

Group III-nitride semiconductors (GaN, AlN, InN) serve as foundational materials for modern optoelectronics, high-frequency microelectronics, and next-generation energy harvesting devices. However, traditional high-temperature epitaxy (>700 °C) introduces severe thermal stress, high dislocation densities, and fundamental incompatibility with flexible substrates or CMOS back-end-of-line (BEOL) processes. Plasma-enhanced atomic layer deposition (PEALD) provides a disruptive, ultra-low thermal budget (<300 °C) pathway for atomic-scale precision growth and conformal coating. This review systematically summarizes recent frontiers in PEALD-synthesized Group III-nitrides and 2D/3D polar heterostructures. First, we dissect the microscopic nucleation kinetics, surface bond reconstruction, and impurity suppression mechanisms across diverse substrates, including Si, sapphire, quartz, metals, and flexible polymers. Next, we highlight 2D template-assisted van der Waals epitaxy on graphene and MoS2, and elucidate polarization-driven dipole interactions and band alignment engineering at 2D/3D polar interfaces (e.g., α-In₂Se₃, Janus MoSSe). Furthermore, we comprehensively discuss innovative applications in advanced photovoltaics (as electron transport and passivation layers in perovskite and quantum dot-sensitized solar cells), silicon-based microcavity lasers, high-electron-mobility transistors (HEMTs), and flexible multimodal sensors. Finally, key technological challenges—including the low-thermal-budget paradox, wafer-scale uniformity, and deposition throughput—are addressed alongside future perspectives in area-selective ALD and neuromorphic computing, presenting a cohesive blueprint from underlying physics to macroscopic system integration. Full article

Silicon carbide (SiC) is the leading wide-bandgap semiconductor material, providing mature doping and device fabrication. Additionally, SiC hosts a multitude of optically active point defects (color centers) and is relevant for many applications in quantum technologies. A crucial step towards harnessing the full potential of the SiC platform includes technologies to create color centers with defined localization and density, e.g., to facilitate their coupling to nano-photonic structures and to observe cooperative effects. Here, silicon vacancy centers and divacancies stand out, as no impurity atom is needed, and high-thermal budget annealing steps can be avoided. We characterize the effect of localized, femtosecond laser irradiation of SiC, investigating surface modifications and photoluminescence, including Raman spectroscopy and optical lifetime measurements. We employ commercial, high-purity, semi-insulating substrates and an industrial-grade laser system to explore broader applicability of the method. As a novel approach, we apply femtosecond laser irradiation to SiC substrates with an epitaxial graphene layer and find that the threshold for photoluminescence due to laser treatment is lowered. Full article

High-index silicon surfaces provide anisotropic step networks, reconstruction states, and facet-adjacent geometries that can modify the first stages of III–V heteroepitaxy. This critical review examines GaAs/AlGaAs growth on Si$\left(hhl\right)$ surfaces, with emphasis on the coupled roles of substrate orientation, surface preparation, first-monolayer initiation, and molecular beam epitaxy kinetics. The central viewpoint is that high-index Si can act as an active interfacial template: its anisotropy can bias early nucleation, relaxation, and faceting pathways before any intentional lithographic patterning is introduced. The discussion is anchored in two recent GaAs/Si studies. The first is a matched-condition benchmark comparing Si(001), Si(113), Si(111), and Si(331) under Ga-first and As-first initiation. The second is a Si(331) case study in which Ga pre-exposure followed by low-rate GaAs nucleation yields laterally ordered nanocorrugation/faceting and measurable in-plane optical anisotropy under the explored conditions. Surface-science precedents from adsorbate-induced reconstructions provide additional context for treating the first atomic layer as a meaningful growth variable. These studies point to a broader opportunity: using high-index Si$\left(hhl\right)$ surfaces to link interface chemistry, anisotropic morphology, structural relaxation, and optical response within a common framework for GaAs/Si integration. Full article

Pulsed laser-induced phase change in silicon underpins applications from photonic device trimming to stealth dicing, yet predictive models that capture the non-equilibrium kinetics governing the competition between epitaxial recrystallization and amorphization remain limited. In this work, we developed a two-dimensional axisymmetric numerical model at the continuum level for picosecond laser-induced melting, resolidification, and amorphization of crystalline silicon at 532 nm laser wavelength, coupling transient heat conduction with Wilson–Frenkel interface kinetics and Lagrangian marker-based interface tracking. The model predicts a bounded amorphization window defined by lower and upper fluence thresholds, within which the central amorphous thickness exhibits a bell-shaped fluence dependence. Under a Gaussian beam, this window governs a morphological transition from a central amorphous spot to an amorphous ring. The predicted amorphization threshold of ≈0.22 J/cm² agrees with published experimental data for 20 ps, 532 nm irradiation. Parametric studies reveal that reducing the spot diameter or substrate temperature shifts or eliminates the upper threshold, transforming the bounded window into a monotonically increasing function, while increasing the pulse duration narrows the window symmetrically until collapse. These results provide quantitative guidelines for selecting irradiation parameters to control phase change in silicon photonic and laser processing applications. Full article

To address the main challenges in thickness estimation of SiC epitaxial layers from infrared reflectance spectra, including refractive index dispersion, multi-beam interference, and spectral uncertainty, this study develops a physics-constrained inversion framework for reflectance spectrum-based analysis. For the measured spectra, Savitzky–Golay filtering is first used to suppress spectral noise, and Gaussian fitting is then employed to improve the localization of interference extrema. The Sellmeier equation is introduced to characterize refractive index dispersion, and the layer thickness is obtained together with the dispersion parameters through nonlinear least squares fitting. To account for spectra affected by higher-order internal reflections, a multi-feature confidence-based identification strategy is further constructed, and an adaptive filtering procedure is introduced for multi-beam interference correction. A Monte Carlo perturbation analysis with ±0.1% peak perturbations and Gaussian noise is additionally performed to assess the robustness of the inversion results. Using SiC datasets measured at two incident angles, the proposed framework reduces the inter-angle deviation of the thickness estimates from 1.14% to 0.08% after multi-beam correction. The results support the effectiveness and robustness of the proposed workflow for the main SiC application scenario considered in this study. In addition, silicon wafer spectra are included as a supplementary transfer test to examine whether the multi-beam identification and correction strategy can be applied beyond the SiC example, rather than as a comprehensive cross-material validation of the framework. Full article

The crystallinity of cubic silicon carbide (3C-SiC) epilayers is improved through the use of a novel wafer bonding and regrowth technique resulting in a reduction in planar defects. The process involves the epitaxial growth of a 3–6 µm thick 3C-SiC seed on silicon (Si), which is polished and bonded to a new handle wafer before the original substrate and defective interface region of the 3C-SiC epilayer are removed. Further epitaxial growth on this Bonded Switchback template results in higher quality 3C-SiC epilayers through the reduction in crystal mosaicity, stacking fault defects, and elimination of interface voids. The process could be applied to 3C-SiC grown on both on- and off-axis substrates, and the form of the new handle has no impact on the growth process, enabling this technology to be applied to sapphire or hexagonal 4H-SiC substrates. The use of such substrates would overcome the thermal budget limitations of Si substrates for 3C-SiC heteroepitaxy and ion implantation. Bonded Switchback can improve material quality for applications in power electronics, as well as see the heterogeneous integration of 3C-SiC into other device structures, potentially leading to a new range of hybrid 3C-SiC/Si devices without the high density of defects observed at the interface between these two materials. Full article

The dynamics of initial layer-by-layer growth and subsequent nucleation of quantum dots of Si and Ge on Si(001) were studied combining reflection high-energy electron diffraction, scanning electron microscopy and atomic force microscopy. It was shown that the processes occurring at the initial stage determine further growth of the heterostructure and final shape and density of nanoislands. The mechanisms of terrace formation, occurrence and dynamics of dimer rows of the 2 × N superstructure, and effects of temperature on the growth characteristics were described. The obtained experimental dependences show the critical relationship between the synthesis parameters (growth temperature), epitaxial growth processes and the characteristics of the resulting nanoislands. The fundamental studies conducted make it possible to create self-organizing quantum dots of a given size and density for advanced optoelectronics, including infrared photosensitive elements and single-photon detectors. Full article

Silicon carbide (SiC) has emerged as a highly attractive material for microelectromechanical systems (MEMS) operating in harsh environments, owing to its outstanding mechanical, thermal, and chemical properties. This review provides a comprehensive overview of the advantages and limitations of SiC-based MEMS, with particular emphasis on the strong interdependence between material structure, mechanical properties, and epitaxial growth processes. The role of defects, residual stress, and crystal quality is discussed in relation to device performance and reliability. Special attention is devoted to cubic SiC grown on silicon substrates, highlighting how growth-induced features influence the mechanical response of micromachined structures. Furthermore, a detailed analysis of the quality factor (Q-factor) is presented for 3C-SiC (111)/Si resonators, including the development of analytical models and their validation through numerical simulations performed using COMSOL Multiphysics (Version 6.1). The necessity of incorporating anisotropic loss factors in numerical modeling is demonstrated to be essential for accurately describing the experimentally observed behavior. This review aims to provide design guidelines and modeling strategies for the optimization of SiC MEMS, supporting their further development for high-performance and extreme-environment applications, including pressure sensors, mechanical resonators and high-stress-tolerant sensors. Full article

SiSn alloys have attracted growing interest for group-IV bandgap engineering, although their epitaxial growth remains challenging due to the extremely low equilibrium solubility of Sn in Si. In this work, fully strained (pseudomorphic) SiSn epitaxial layers were grown on Si (001) substrates by means of molecular beam epitaxy. A systematic investigation reveals a strong inverse correlation between growth temperature and Sn incorporation efficiency. Despite a constant Sn flux, the incorporated Sn composition decreases from 5.5% to 3.2% as the growth temperature increases, indicating a pronounced temperature dependence of Sn incorporation. Reflection high-energy electron diffraction indicates a gradual transition of the growth from two-dimensional to three-dimensional with increasing film thickness. Structural characterization by means of X-ray diffraction, atomic force microscopy, and transmission electron microscopy confirms the pseudomorphic growth and smooth surface morphology and reveals twins and stacking faults near the surface region. These results establish a quantitative reference for SiSn growth kinetics and provide guidance for future studies of SiSn and SiGeSn alloys in silicon-compatible electronic and optoelectronic applications. Full article

Silicon-based germanium films are promising for the fabrication of low-power, high-performance electronic and optoelectronic devices. In this work, we report an effective approach for directly growing Ge films with ultrahigh carrier mobility on Si (001) substrates using molecular beam epitaxy (MBE). Strain relaxation of the germanium films is realized through the formation of partial dislocations and 90° misfit dislocations at the Ge/Si interface. The Ge film exhibits a smooth surface with a root-mean-square roughness of 0.187 nm and a low threading dislocation density of only 1.2 × 10⁷ cm⁻². Hall effect measurements reveal a high room-temperature mobility of up to 1916 cm²V⁻¹s⁻¹ along with a carrier concentration of 1.425 × 10¹⁶ cm⁻³. These findings demonstrate that MBE-grown Ge films, possessing exceptionally high carrier mobility, hold great promise for integration into advanced electronic and optoelectronic devices. Full article

Single-Event Burnout (SEB) is one of the most critical failure mechanisms in silicon power MOSFETs operating in radiation environments, particularly under heavy-ion irradiation, and often limits device operation through excessive voltage derating. In this work, SEB robustness of a silicon VDMOS power device is investigated using detailed electro-thermal transient simulations. The study evaluates two complementary device-level modifications: the introduction of a buffer layer between the epitaxial layer and the substrate, which has been reported in the past, and a new approach considering the incorporation of a novel highly doped boron BOX implant within the P-body region. Heavy-ion impacts are simulated using a physically based model implemented in SENTAURUS TCAD, accounting for ion energy deposition, impact position, and thermal effects. The results show that the buffer layer increases the second breakdown voltage and can suppress high-current operating points, while the BOX implant raises the parasitic BJT activation threshold by reducing the P-body resistance. When combined, both modifications lead to a significant reduction in the peak temperature reached during after-impact transients, without introducing measurable degradation of static electrical characteristics. These results demonstrate that combining buffer layer engineering with localized P-body resistance reduction is an effective strategy to improve SEB robustness in silicon VDMOS power devices without relying on excessive derating. Full article

Silicon carbide (SiC) is the leading wide bandgap semiconductor for high-power and high-temperature electronics, but the high defect density still limits device performance. This study investigates how inclusions, Basal Plane Dislocations (BPDs), and Threading Screw Dislocations (TSDs) in 4H-SiC substrates affect epitaxial defect formation. Twenty 200 mm SiC wafers were analyzed after epitaxial growth in two industrial Chemical Vapor Deposition (CVD) reactors, one using Trichlorosilane/Ethylene (Reactor A) and the other Silane/Propane (Reactor B). Defects were characterized using Candela (KLA), Altair (KLA), XRTmicron LAB (Rigaku), SICA (Lasertec), and Crossbeam (ZEISS) dual-beam SEM system. Statistical correlation showed that the conversion rate of embedded particles decreases with particle depth and increases with particle size. Reactor A exhibited lower propagation rates, indicating better suppression of substrate-related defects. SEM/FIB-EDX analyses suggested that carbon inclusions generate pits while metallic inclusions induce triangular defects. Dislocation analysis confirmed a strong correlation between TSDs and BPDs with carrots and triangular defects. BPD conversion rates were estimated at about 98.3% (Reactor A) and 99.8% (Reactor B). These results emphasize the importance of substrate quality and buffer layer optimization to minimize defect propagation. Full article

To improve the process controllability and fabrication uniformity of porous silicon (PS)-based electron emission devices (EEDs), we employed an epitaxial (epi) silicon film as the functional layer, leveraging its advantages of high crystalline quality and flexibility of resistivity modulation regardless of the substrate. Precise modulation of the epi film resistivity was achieved via ion implantation. We investigated the effects of resistivity modulation on the fabrication process and device performance. This scheme enabled the formation of PS through electrochemical etching without illumination, and therefore etch self-termination. As a direct result, the etching uniformity in both the vertical and horizontal directions is enhanced. It then facilitated the optimization of the oxidation of the PS surface, which is essential for EED performance. The devices exhibited a maximum electron emission current density (J_e) of 80 μA/cm² with high stability. Driven under DC mode at a bias voltage (V_ps) of 23 V, J_e decreased temporarily to 28 μA/cm² after 4 h of continuous operation. This study provides a new feasible approach for research on PS EEDs. Full article

The chemical vapor deposition (CVD) method is a key technology for producing silicon carbide (SiC) epitaxial wafers used in high-performance power devices. Defects in the epitaxial wafers, such as triangular, threading dislocations (TDs); basal plane dislocations (BPDs); and stacking faults (SFs), are considered the critical bottleneck determining device performance and long-term reliability. This review aims to systematically elucidate the fundamental physical and chemical principles underlying defect generation during epitaxial growth of SiC by CVD and provide a comprehensive assessment of corresponding defect reduction strategies. Starting from the essential condition of thermodynamic growth, we analyze the main mechanisms of defect formation, including nonequilibrium kinetics, surface reaction kinetics, and the inheritance of substrate defects. Emphasis is placed on discussing the mechanisms and methods for suppressing defect formation through substrate engineering (off-angle design and surface pretreatment), precise control of the growth parameters (C/Si ratio, temperature, gas composition, and so on), as well as advanced post-treatment techniques. This leads to the proposal of practical strategies focusing on substrate engineering and growth parameter optimization toward practical application. Finally, we summarize the inspection techniques and outline future research directions toward intrinsic low-defect-density SiC epitaxial materials for high-voltage applications. Full article

Dislocation reduction in gallium nitride (GaN) epitaxial layers remains a critical challenge for high-performance GaN-based electronic devices. In this study, GaN epitaxial growth on newly-developed 4H-Silicon Carbide (SiC) meta-substrates was systematically investigated to elucidate the role of surface pattern geometry in modulating dislocation propagation. A series of truncated-hexagonal-pyramid meta-structures with a fixed array period and varying pattern ratios (R) were designed and fabricated to enable controlled tuning of the effective surface morphology. Atomic force microscopy confirmed comparable surface flatness for all samples after epitaxial growth. Cathodoluminescence analysis revealed a non-monotonic dependence of defect density on R, indicating the existence of an optimal pattern geometry. Among all configurations, the outstanding sample exhibited the lowest defect density, achieving a 54.96% reduction in threading dislocations (edge + mixed) compared with a planar reference. Cross-sectional transmission electron microscopy further confirmed a substantially reduced dislocation density and clear evidence of dislocation bending and termination near the meta-structured regions. These results demonstrate that geometry-engineered 4H-SiC meta-substrates provide an effective and scalable strategy for dislocation modulation in GaN epitaxy on SiC meta-substrates, offering a promising pathway toward advanced GaN power and RF devices. Full article